This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. MtrA is a 10-heme cytochrome from the bacteria, Shewanella oneidensis. No crystal structure yet exists for this protein. A recently proposed hypothesis suggests that it is a highly asymmetric protein with an aspect ratio of ~ 4:1, which would allow parallel stacking of the hemes. Determination of its radius of gyration and low-resolution solution structure with SAXS will allow us to investigate this hypothesis and further understand the mechanism of electron transfer in this protein.